In a top-blow type outdoor unit for an air-conditioning apparatus, a propeller fan is arranged in an upper portion of a casing, and a heat exchanger is arranged in the casing. Further, in the top-blow type outdoor unit for an air-conditioning apparatus, an airflow generated through the rotation of the propeller fan passes through the heat exchanger so that heat is exchanged between outside air and refrigerant flowing through the heat exchanger. Normally, an air velocity becomes higher at a position closer to the propeller fan. Accordingly, the air velocity in an upper portion of the heat exchanger is higher than the air velocity in a lower portion of the heat exchanger, with the result that an air velocity distribution in the heat exchanger is uneven. When the air velocity distribution in the heat exchanger is uneven, efficiency of heat exchange in the heat exchanger is reduced.
Hitherto, in order to reduce unevenness of an air velocity distribution in a heat exchanger, there has been proposed a top-blow type outdoor unit including a cylindrical duct arranged in an internal space in an upper portion of the outdoor unit. With this configuration, airflow resistance in an upper portion of the heat exchanger is increased as compared to the airflow resistance in a lower portion of the heat exchanger (for example, see Patent Literature 1).